Common Conversions:
Most of the world has converted to the metric system of measurement [mili-meter, meter, kilometer, liter, gram, kilogram ...], but the U.S. is the only significant holdout. It and a few of it's Caribbean neighbors are still on the English Customary Weights and Measures [inch, foot, yard, mile, gallon, pound, ...]. Size/distance measure in this system is refered to as standard, Inch or SAE (Society of Automotive Engineers)

* kcal - kilocalorie = Amount of heat
requird to raise one kilogram of water
by one degree Celsius.
The small calorie (gram calorie) is 1/1000 kcal.
Sometimes Calorie (capital C) is used to distinguish kcal from calorie.
When used in the context of food energy the term Calorie generally refers to the kilogram calorie.

Reference Standard:
A kilogram was the mass of water filling a cube that is one-tenth of a meter on each side, or one liter of volume, and a meter was one ten-millionth of the distance from the North Pole to the Equator, along the path passing through Paris (since it was the French Academy of Sciences that defined the meter).

In 1960, scientists defined the meter in terms of the wavelength of a specific orange light emitted by krypton atoms. In 1983, they redefined the speed of light to be exactly 299,792,458 meters per second, so a meter is now just the distance that light travels in a vacuum in 1/299,792,458th of a second.

A platinum-iridium cylinder about the size of a plum LOCKED in a vault in Paris was established as the official definition of the kilogram, in 1889.

In 2005 Scientists at the National Institute of Standards and Technology in Gaithersburg, Md., announced significant progress toward supplanting this cylinder.
It's a two-story-tall contraption that measures the power needed to generate an electromagnetic force that balances the gravitational pull on a kilogram of mass.